I should also mention that my charging light (red battery on the combo meter) never came on while my battery was discharging down to 10V where the car stopped running (i have a cigarette lighter voltmeter to monitor the battery voltage from inside the cabin while driving). I suspect this would have come up during the troubleshooting if I was able to disconnect the battery current sensor to disable the variable voltage control. One of the branches in the troubleshooting tree specifically branches on the condition with light or without. But I didn't continue down those paths to see how that relates to whatever unique failures.
I THOUGHT I "fixed" my battery charging problem
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Checked the fsm for my 06 Infiniti with no variable voltage control. Alternator spec is 14.1-14.7V and it doesn't cook batteries. This is standard alternator output range for most "old" cars. I used to think old cars meant 60-70's but now I guess old is more like early 00's. I think I have an obd dongle and app somewhere that can chart battery voltage and rpm and I'll see if I can chart the Murano vs my other cars. Looking at the cigarette lighter voltmeter (which only has 0.2V resolution) it looks like disabling the variable voltage control makes the voltage hover around 14.2 but sometimes 14.0 and sometimes 14.4. The max and min and long term trend would be more clear with a chart.
06 G35 alternator spec:
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I looked up the alternator spec on the 2006 Murano and was expecting it to be the same type considering the G35 and the Murano use the same VQ35DE but for some reason it's a different alternator (Hitachi vs. Mitsubishi) even though it's the same rating (12V-110A). Maybe it's a mechanical thing because of the transverse engine in the Murano. I've been on that Infiniti forum forever and don't recall anything like the number of charging issue threads I've seen on here in 5 months where people say the car dies while they're driving due to a dead battery. I wonder if the Hitachi alternator design just sucks for some reason. I've never seen an Infiniti post saying they went through 3 batteries and 3 alternators in a couple years but I've seen several threads like that for 1st and 2nd gen Muranos. I also thought the 1st gen Murano might have had the variable voltage control because there were so many posts with problems but I see it's old school fixed output (also 14.1 - 14.7) so that doesn't explain the failures.
06 Murano alternator spec:
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06 G35 alternator spec:
I looked up the alternator spec on the 2006 Murano and was expecting it to be the same type considering the G35 and the Murano use the same VQ35DE but for some reason it's a different alternator (Hitachi vs. Mitsubishi) even though it's the same rating (12V-110A). Maybe it's a mechanical thing because of the transverse engine in the Murano. I've been on that Infiniti forum forever and don't recall anything like the number of charging issue threads I've seen on here in 5 months where people say the car dies while they're driving due to a dead battery. I wonder if the Hitachi alternator design just sucks for some reason. I've never seen an Infiniti post saying they went through 3 batteries and 3 alternators in a couple years but I've seen several threads like that for 1st and 2nd gen Muranos. I also thought the 1st gen Murano might have had the variable voltage control because there were so many posts with problems but I see it's old school fixed output (also 14.1 - 14.7) so that doesn't explain the failures.
06 Murano alternator spec:
No aftermarket anything on this car and only oem cable connected to neg battery terminal. It's in pretty good shape and tightens up nicely. When I bought this mess, I went through the engine bay and cleaned everything particularly the negative cable because of all the threads that say it can be responsible for charging problems (which I knew this car had). I sanded the cvt boss and batt neg cable ring lug to shiny metal and bonded with de-ox grease to prevent future corrosion. Also sanded the ring lug to shiny metal at the chassis connection but didn't sand the painted frame mounting point (which seems like a crazy way to ground something because that paint is not conductive, UL prohibits grounding to painted surfaces in commercial power supply products). I did the same for every ground I could find like the coil grounds on the top and the mystery harness grounds along the frame under the air box etc.
I got the obd dongle out that I bought years ago to diagnose some o2 sensor codes. I can't believe I didn't do this sooner. It can monitor a ton of Murano specific PIDs that my Infiniti doesn't have. Bunch of CVT parameters that they'll show you glimpses of but you gotta pay to collect it continuously. Basic stuff is free. It's cool that this works for ios because I still don't have an android device to use for my cars. Here's the data I collected on my drive to work. This is the whole 5m commute from driveway to parking lot. That long flat line is me waiting at one of two traffic lights between work and home. I'll chart my Infiniti and Toyota soon and see how the charging profile compares. I'm thinking they're going to look the same. I don't think this kills batteries. This is regular car charging that's been used for decades until the manufacturers made them "smart".
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I got the obd dongle out that I bought years ago to diagnose some o2 sensor codes. I can't believe I didn't do this sooner. It can monitor a ton of Murano specific PIDs that my Infiniti doesn't have. Bunch of CVT parameters that they'll show you glimpses of but you gotta pay to collect it continuously. Basic stuff is free. It's cool that this works for ios because I still don't have an android device to use for my cars. Here's the data I collected on my drive to work. This is the whole 5m commute from driveway to parking lot. That long flat line is me waiting at one of two traffic lights between work and home. I'll chart my Infiniti and Toyota soon and see how the charging profile compares. I'm thinking they're going to look the same. I don't think this kills batteries. This is regular car charging that's been used for decades until the manufacturers made them "smart".
G35 with no variable voltage control charging looks the same as Murano w/disabled vvcs. The G35 is even a little higher averaging more like 14.5 where Murano w/disabled VVCS was more like 14.3.
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Youtube recommended this QX56/80 video to me because of all the alternator debug videos I watched. This guy just cuts his control wire to disable the vvcs. Lots of commenters complaining of repeated dead battery replacements in these vehicles. I'm convinced disabling this system is a win for reliability with no negative impact on battery life at least compared to pre-vvcs vehicles. Jury's still out on tradeoff with mileage but these cars aren't really all that fuel efficient to begin with and not the reason I own it. I averaged 20mpg before disable. Unless my efficiency suffered to something like 17mpg, I think I'd still live with it like this because I don't want my kids getting stranded when they're new drivers. If it dropped below 17mpg I might go to the trouble of trying to debug further and figure out which piece isn't working right and see if I could fix it. If it turns out not to be caused by vvcs malfunction (other alternator defect, wiring/grounding problem etc.) it'll happen again despite me disabling vvcs and I'll be forced to deal with it if my kids are going to be able to use this car confidently. Three months to go before my oldest starts driving.
Youtube recommended this QX56/80 video to me because of all the alternator debug videos I watched. This guy just cuts his control wire to disable the vvcs. Lots of commenters complaining of repeated dead battery replacements in these vehicles. I'm convinced disabling this system is a win for reliability with no negative impact on battery life at least compared to pre-vvcs vehicles. Jury's still out on tradeoff with mileage but these cars aren't really all that fuel efficient to begin with and not the reason I own it. I averaged 20mpg before disable. Unless my efficiency suffered to something like 17mpg, I think I'd still live with it like this because I don't want my kids getting stranded when they're new drivers. If it dropped below 17mpg I might go to the trouble of trying to debug further and figure out which piece isn't working right and see if I could fix it. If it turns out not to be caused by vvcs malfunction (other alternator defect, wiring/grounding problem etc.) it'll happen again despite me disabling vvcs and I'll be forced to deal with it if my kids are going to be able to use this car confidently. Three months to go before my oldest starts driving.
My 02 Sequoia (w/o vvcs) regulates a little lower than my Nissan vehicles. Seems to average about 14.0 compared to 14.5 for the G35 and 14.3 for the Murano w/no vvcs. I don't have an FSM for it so can't tell what kind of alternator is has or its specs. I get various search results so not sure without an actual Toyota reference. I think all these numbers from 14-14.5 are pretty typical for cars produced prior to introduction of vvcs. This was a 20min drive all on streets with speed limits like 30-45mph.
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The intermittent no charge condition is back despite disabling vvcs. Luckily this time I was paying more attention and felt a slight hiccup in rpm while sitting at a light and looked down at my cigarette lighter voltmeter and could see the voltage falling from 14 to 13 to 12. I wasn’t far from home so I was able to make it back to the house without getting stranded. No alternator light or cel. When I tried to connect my obd reader it wouldn’t connect to the ecu even though the car was still running. I got home and popped the hood and about the time I put voltmeter probes on the battery I heard the fans kick on and the no charge condition went away and battery voltage went back to 14V. I jiggled the alternator harness to see if something was loose there but couldn't produce any change but access is tough and it's hard to stick your hands in there because everything is hot. So I went for a drive and the no charge condition came back right away but this time I was able to collect some data because the tool would connect when everything was running right but eventually you lose comm when the problem pops up and the voltage drops low enough. My handheld wired Innova code reader could connect even when my wireless dongle couldn't so don't really know what's up with that. I don't get any data logging with the Innova so I use the wireless mostly.
So I'm back to the drawing board and will have to go back to troubleshooting the no charge condition the proper way. Gotta start with finding a way to unplug the battery current sensor. I don't know what the Nissan Starter/Charging Tester is exactly but I'm confident my condition is NO charging voltage rather than LOW because it will be down to 10V in <10miles if you don't get lucky and the condition goes away on its own or you hook up an external charger. I read through the troubleshooting and most of it ends with REPLACE ALTERNATOR (fun!). If it gets to there I may try and rebuild it if I can find service parts just to see if I can actually figure out what is failing in these things.
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So I'm back to the drawing board and will have to go back to troubleshooting the no charge condition the proper way. Gotta start with finding a way to unplug the battery current sensor. I don't know what the Nissan Starter/Charging Tester is exactly but I'm confident my condition is NO charging voltage rather than LOW because it will be down to 10V in <10miles if you don't get lucky and the condition goes away on its own or you hook up an external charger. I read through the troubleshooting and most of it ends with REPLACE ALTERNATOR (fun!). If it gets to there I may try and rebuild it if I can find service parts just to see if I can actually figure out what is failing in these things.
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